Fluorescent lamp and method of manufacturing same

Abstract

A cold cathode fluorescent tube where an electron emitting electrode is sealed in shows much deterioration in the luminance with time, thereby being not adequate for a long time use. The electrode emitting electrode is formed in such a shape that an electric field is not locally concentrated. By mixing a material of high heat conductivity, such as tungsten, as the material for the electron emitting electrode or using helium of high heat conductivity as the sealing gas, a long life of the cold cathode fluorescent tube is achieved.

1. A fluorescent lamp comprising an electron emitting electrode, wherein:
 said electron emitting electrode has a portion that is formed by using a mixture of at least one material selected from the group consisting of La 2 O 3 , ThO 2 , and Y 2 O 3  and a metal having a thermal conductivity higher than that of said selected material; and 
 wherein the electron emitting electrode has an open tip end substantially defined by a hyperbolic function. 
 
   
   
     2. The fluorescent lamp according to  claim 1 , wherein said material having higher thermal conductivity is tungsten (W). 
   
   
     3. The fluorescent lamp according to  claim 2 , wherein said electron emitting electrode is made of the same material as that of a lead wire which supplies a voltage to said electrode. 
   
   
     4. The fluorescent lamp according to  claim 2 , wherein at least one of La 2 O 3 , ThO 2 , and Y 2 O 3  is contained in a volume ratio of 0.001 to 0.5 relative to W. 
   
   
     5. The fluorescent lamp according to  claim 2 , wherein said at least one of La 2 O 3 , ThO 2 , and Y 2 O 3  is contained in a volume ratio of 0.01 to 0.1 relative to W. 
   
   
     6. The fluorescent lamp according to  claim 1 , wherein a portion, contacting a tube wall, of said electron emitting electrode does not contain said selected material. 
   
   
     7. The fluorescent lamp according to  claim 1 , comprising a tube is filled with a gas, wherein said gas contains at least one of He and H 2 . 
   
   
     8. The fluorescent lamp according to  claim 1 , wherein said portion contains, by weight, 1 to 10% of said selected material. 
   
   
     9. The fluorescent lamp according to  claim 8 , wherein said portion contains, by weight, 5 to 7% of said selected material. 
   
   
     10. The fluorescent lamp according to  claim 1 , wherein the fluorescent lamp is a cold cathode fluorescent lamp. 
   
   
     11. A fluorescent lamp comprising an electron emitting electrode having a hollow cathode structure, wherein said electron emitting electrode has an open tip end of an obtuse angle shape or a curved shape, and wherein said open tip end of said electron emitting electrode has a shape substantially defined by a hyperbolic function. 
   
   
     12. The fluorescent lamp according to  claim 11 , wherein at least said open tip end of said electron emitting electrode is formed by using a mixture of at least one material selected from the group consisting of La 2 O 3 , ThO 2 , and Y 2 O 3  and W. 
   
   
     13. A fluorescent lamp electrode for use in a fluorescent lamp, formed by a mixture of at least one material selected from the group consisting of La 2 O 3 , ThO 2 , and Y 2 O 3  and W;
 the fluorescent lamp electrode having an open tip end substantially defined by a hyperbolic function. 
 
   
   
     14. A method of manufacturing a fluorescent lamp comprises a step of cleaning in the state where the inside of a tube is filled with a cleaning liquid, wherein said step of cleaning performs the cleaning by reciprocating said cleaning liquid in the tube at a pressure higher than a normal pressure;
 the method further comprising a step of mounting, within the tube, a fluorescent lamp electrode having an open tip end substantially defined by a hyperbolic function. 
 
   
   
     15. A method of manufacturing a fluorescent lamp including a step of drying by raising a temperature to desorb moisture inside a tube, characterized in that said step of drying is performed while feeding a dry gas through the inside of the tube;
 the method further comprising a step of mounting, within the tube, a fluorescent lamp electrode having an open tip end substantially defined by a hyperbolic function. 
 
   
   
     16. The method of manufacturing a fluorescent lamp according to  claim 15 , wherein said dry gas is a nitrogen gas, a dry air, argon, or oxygen. 
   
   
     17. A method of manufacturing a fluorescent lamp including a step of exhausting a gas inside a tube, and a step of introducing an oxygen-free dry gas into said tube, wherein said steps are alternately repeated;
 the method further comprising a step of mounting, within the tube, a fluorescent lamp electrode having an open tip end substantially defined by a hyperbolic function. 
 
   
   
     18. The method of manufacturing a fluorescent lamp according to  claim 17 , wherein said dry gas is a nitrogen gas or an argon gas. 
   
   
     19. The method of manufacturing a fluorescent lamp according to  claim 17 , wherein said fluorescent lamp is used as a cold cathode fluorescent lamp.